The four main types
| Type | Support | Pressure relief | Folds easily | Weight |
|---|---|---|---|---|
| Innerspring | Fair | Limited | Fair | Heavier |
| Memory foam | Fair | Good | Very good | Medium |
| Hybrid (coil and foam) | Good | Good | Fair | Heavier |
| Air-over-coil | Good | Fair | Fair | Medium |
Innerspring
Metal coils with a thin layer of padding. This is the traditional pull-out mattress. It's supportive when new, but thin padding means you can feel the coils and, on tri-fold frames, the bars beneath. Pocketed coils (each spring in its own fabric sleeve) feel less bouncy than open coils.
Memory foam
Foam that softens with body heat and moulds to your shape. It folds well, so it suits tri-fold frames, and it hides the frame better than thin innerspring. Lower-density foam can feel warm and lose its shape sooner. If the specification lists foam density, higher density usually lasts longer.
Hybrid
A layer of coils with foam above. Hybrids balance support and comfort and are a common upgrade for frequently used sofa beds. They are thicker and heavier, so check that the mechanism is rated for the mattress you choose.
Air-over-coil
An inflatable chamber sits on top of a coil or foam base inside the mattress. You inflate it with a pump when you open the bed and let the air out before folding it away. The air layer lifts you off the frame and lets you adjust firmness. You need access to a power socket, and the pump is one more part that can fail.
Typical thickness by mechanism
| Mechanism | Typical mattress thickness |
|---|---|
| Tri-fold pull-out | About 11 to 15 cm (4.5 to 6 in) |
| Bi-fold pull-out | About 14 to 20 cm (5.5 to 8 in) |
| Click-clack / futon | The seat and back upholstery, or a futon of about 12 to 20 cm (5 to 8 in) |
| Daybed and trundle | A standard single mattress, often 15 to 25 cm (6 to 10 in); trundles usually take a thinner one |
| Wall bed | A normal mattress within the maximum thickness the frame allows |
These are typical ranges, not rules. A thicker mattress than the frame allows can stop the bed from closing or strain the mechanism. Always use the maximum thickness in the product's specification.
Replacing a sofa bed mattress
- Measure the existing mattress length, width and thickness, and the inside of the frame.
- Check the maximum thickness the mechanism will close with. Ask the maker if it isn't printed.
- Choose a mattress made for sofa beds, which is designed to fold. A standard bed mattress cut to size won't fold the same way.
Toppers
A topper of 5 to 8 cm (2 to 3 in) laid over the mattress when the bed is open is the cheapest comfort upgrade for an occasional guest bed. Store it rolled with the bedding rather than folding it into the frame, unless the specification says it will fit.